Unforgiveness receives no accolades but it comes to steal our joy, make us miserable pharisees and keep us from living. They were right to hold onto grievances because, surely, that is justice, but the soul becomes indignant and absorbed by negativity and pain, not excluding physiological pain. Ill will ties one to the very thing said person wants to separate from, allowing for open sores and allowed vices to fester.
In other words, unforgiveness cuts relationships, drives us to loneliness and isolates us from people who actually give us proper concern. This blinds the soul and hinders one from being able to trust or love or to let their self be trusted and loved. Little by little all these emotions add up and the physical symptoms appear in form of anxiety, depression and stress related diseases. Research also shows that resentment leads to high blood pressure and suppresses the immune system which is some of the impacts.
Also, unforgiveness leads to loss of spiritual growth. So, by holding the grudge, one shuts himself from the growth lessons and possibilities that life presents. It prevents us from being able to see the real beauty in forgiving and getting back on the right track and to be able to live a free life.
Remember, forgiveness is not excusing a wrong doer but freeing yourself from the loss of the headache. It is an opportunity which you offer to yourself that is a liberation from the jail of suffering. Forgive and set free yourself from the hazards of resentment because it will set your soul free.